Trying to find importance of resistance measurements.

I tested newly bought / rebuilt injectors against the original ones that I am going to have cleaned.

7 of the 8 rebuilt ones read 16.2 ohms give or take .2
1 was 14.8

Stock injectors were all 16.2 give or take .2

Five O website states 14.5.

Is more resistance bad in this case?
Higher resistance result in slower/delayed response?

Thanks

 

I did some research on this subject matter when I first started "shark tuning". The main point I took from that was that all the injectors should have resistance values within about 0.5 ohms so variance of 0.2 ohms would be fine but not the measured difference with the seemingly "rogue" injector. As to what [if any] error that difference will introduce I know not.

One also has to be wary about the accuracy/resolution of the multi meter you are using but I doubt that will be a factor here given we are talking about differences..

 

An injector is a solenoid that simply manages a sequential flow or blockage of fuel passing an orifice. The resistance is pretty much meaningless unless it is so low that the injector driver can't generate the current to throw the tiny solenoid slug. If the min value is 14-ish ohms, and you are getting 14-ish ohms you are good to go. It is in effect, a binary state device. Closed, or open.

If one wants to get into the minutia of edge rates, ringing, slew rate, capacitive reactance we can do that, but it's complete bullspit.

 

Like Doc said, the actual resistance is not particularly important. The LH isn't going to care about 14 ohms versus 16. (It will care about a low-impedance injector, don't ever make that mistake).

But it is important to understand that the resistance of an injector is a function of the wire used to wind the solenoid coil-- length, wire-gauge, etc. And there is absolutely no reason why a batch of injectors that are all manufactured by the same process should vary much at all. For example, seven of your injectors are 16.2 ohms plus/minus not much. That's what I would expect, and the resistance of a test-probe can be 0.2 ohms.

Now you gotta ask yourself, why is one different than the others? If it is the same type of injector made by the same factory then it should be the same resistance. So either (a) they slipped in an injector from a different factory, or a different spool of wire, or a different something. And if that something is different, then it may not behave the same in terms of opening/closing time. Or, it could be a shorted coil, with portion of the coil windings bypassed by an internal short. That will change the magnetic characteristics and change the opening/closing time.

In any event, injector shops don't generally check opening-time, it is a nuisance. And good shops will swap injectors around trying to match the static flow rate, so it may simply be an injector from a different batch. But an injector with a matched static flow rate with a mis-matched impedance doesn't mean they are matched for opening/closing time and dynamic performance.

Getting proper injectors is hard enough, at least you want to get eight that are all the same. If you do use this batch then make a note of where the oddball got installed, and then keep an eye on the spark plugs and see if you see any difference.

 

Thanks Gents,

Clears up that dilemma.

Until the next time..

Much appreciated.